How to Convert a PDF to Text via Optical Character Recognition in Node.JS

Downloading an important PDF document only to have it not scan properly as text has been personal pet peeve both as a student and professionally. With the inability to copy and paste or edit the PDF, your time may be eaten up by tedious transcription that may have otherwise been avoided. The following API, however, will mitigate this issue using Optical Character Recognition to convert the PDF to text that can then be utilized more fully.

To start our function, we first need to run this command to install the SDK:

npm install cloudmersive-ocr-api-client --save

Or, you can add this snippet to your package.json:

"dependencies": {
    "cloudmersive-ocr-api-client": "^1.3.3"
  }

Then, we can call our function:

var CloudmersiveOcrApiClient = require('cloudmersive-ocr-api-client');
var defaultClient = CloudmersiveOcrApiClient.ApiClient.instance;
// Configure API key authorization: Apikey
var Apikey = defaultClient.authentications['Apikey'];
Apikey.apiKey = 'YOUR API KEY';
var apiInstance = new CloudmersiveOcrApiClient.PdfOcrApi();
var imageFile = Buffer.from(fs.readFileSync("C:\\temp\\inputfile").buffer); // File | PDF file to perform OCR on.
var opts = { 
  'recognitionMode': "recognitionMode_example", // String | Optional; possible values are 'Basic' which provides basic recognition and is not resillient to page rotation, skew or low quality images uses 1-2 API calls per page; 'Normal' which provides highly fault tolerant OCR recognition uses 14-16 API calls per page; and 'Advanced' which provides the highest quality and most fault-tolerant recognition uses 28-30 API calls per page.  Default recognition mode is 'Basic'
  'language': "language_example", // String | Optional, language of the input document, default is English (ENG).  Possible values are ENG (English), ARA (Arabic), ZHO (Chinese - Simplified), ZHO-HANT (Chinese - Traditional), ASM (Assamese), AFR (Afrikaans), AMH (Amharic), AZE (Azerbaijani), AZE-CYRL (Azerbaijani - Cyrillic), BEL (Belarusian), BEN (Bengali), BOD (Tibetan), BOS (Bosnian), BUL (Bulgarian), CAT (Catalan; Valencian), CEB (Cebuano), CES (Czech), CHR (Cherokee), CYM (Welsh), DAN (Danish), DEU (German), DZO (Dzongkha), ELL (Greek), ENM (Archaic/Middle English), EPO (Esperanto), EST (Estonian), EUS (Basque), FAS (Persian), FIN (Finnish), FRA (French), FRK (Frankish), FRM (Middle-French), GLE (Irish), GLG (Galician), GRC (Ancient Greek), HAT (Hatian), HEB (Hebrew), HIN (Hindi), HRV (Croatian), HUN (Hungarian), IKU (Inuktitut), IND (Indonesian), ISL (Icelandic), ITA (Italian), ITA-OLD (Old - Italian), JAV (Javanese), JPN (Japanese), KAN (Kannada), KAT (Georgian), KAT-OLD (Old-Georgian), KAZ (Kazakh), KHM (Central Khmer), KIR (Kirghiz), KOR (Korean), KUR (Kurdish), LAO (Lao), LAT (Latin), LAV (Latvian), LIT (Lithuanian), MAL (Malayalam), MAR (Marathi), MKD (Macedonian), MLT (Maltese), MSA (Malay), MYA (Burmese), NEP (Nepali), NLD (Dutch), NOR (Norwegian), ORI (Oriya), PAN (Panjabi), POL (Polish), POR (Portuguese), PUS (Pushto), RON (Romanian), RUS (Russian), SAN (Sanskrit), SIN (Sinhala), SLK (Slovak), SLV (Slovenian), SPA (Spanish), SPA-OLD (Old Spanish), SQI (Albanian), SRP (Serbian), SRP-LAT (Latin Serbian), SWA (Swahili), SWE (Swedish), SYR (Syriac), TAM (Tamil), TEL (Telugu), TGK (Tajik), TGL (Tagalog), THA (Thai), TIR (Tigrinya), TUR (Turkish), UIG (Uighur), UKR (Ukrainian), URD (Urdu), UZB (Uzbek), UZB-CYR (Cyrillic Uzbek), VIE (Vietnamese), YID (Yiddish)
  'preprocessing': "preprocessing_example" // String | Optional, preprocessing mode, default is 'Auto'.  Possible values are None (no preprocessing of the image), and Auto (automatic image enhancement of the image before OCR is applied; this is recommended).
};
var callback = function(error, data, response) {
  if (error) {
    console.error(error);
  } else {
    console.log('API called successfully. Returned data: ' + data);
  }
};
apiInstance.pdfOcrPost(imageFile, opts, callback);

As you can see within the code block, the parameters for this API include the required image file (PDF file), as well as the optional recognition mode (basic, normal, and advanced), language, and preprocessing (image enhancement). The possible values for these parameters are included within the code as notes, so be sure that your inputs are valid according to these conditions.

The API Key for this function can be retrieved for free and with no commitment from the Cloudmersive website. This will give you access to 800 calls per month across our entire API library.